Lead refining process



United States Patent 3,041,162 LEAD REFINING PROCESS Eugene H. Euster, 2933 Atlantic-Ava, Longport, NJ. No Drawing. Filed Jan. 14, 1960, Ser. No. 2,357

5 Claims. (Cl. 75-78) The present invention is directed to a lead refining process, and more particularly to a lead refining process in which antimony-free lead may be secured.

The separation of antimony from lead is a most diificult one on a commercial basis. While antimony can be separated from lead by the use of caustic soda or metallic sodium, the relatively high price of these materials renders them commercially useless in terms of removing appreciable quantities of antimony.

This invention has as an object the provision of a novel process for refining lead.

This invention has as a further object the provision of a novel process in which lead of high purity is obtained.

This invention has as a still further object the provision of a novel process in which antimony is separated from lead at relatively low cost.

Other objects will appear hereinafter.

I have discovered that litharge (PbO) has a far higher aflinity for antimony than does lead at the instant in which said litharge is in its nascent form, and at a temperature within the range of about 1275 F. to about 1285 'F., and preferably about l280 Lead which is to be reclaimed or smelted, such as batter lead, or battery plates, and other sources of lead may contain the following impurities: Zinc, copper, tin, and antimony. These impurities should be removed from the lead in the aforesaid order.

There is normally no problem in the removal of zinc from lead. A variety of techniques are available for so doing, and when the smelting of the lead includes treatment within a blast furnace, the zinc is normally removed by exposure to the blast furnace temperature and air blast.

Copper maybe removed from lead by the introduction of sulphur when the lead has been melted at a temperature close to the melting point of the crude lead. Thus, if the molten lead and sulfur is agitated, as by a mechanical agitator, the copper may be separated from the molten lead by skimming the resultant dross.

Alternatively, the copper may be removed from the molten lead by heating the molten lead to a temperature of about 1000 F. with the sludge present in the lead in the form in which the same leaves the blast furnace, and subjecting the mixture of sludge and molten lead to violent agitation. Under conditions of violent agitation, the sludge will be gradual-1y replaced by a black, dry dross which will contain substantially all of the copper contaminant.

Tin may be removed from the copper-cleaned lead by circulating air through the copper-cleaned molten lead at a temperature of about 1275 F. to about 1285 F. As long as there is any appreciable quantity of tin within the molten lead a yellow, dry dross will form on the top of the vessel within which the molten lead is being subjected to air agitation. I have found that as long as such yellow, dry dross forms, there will be no noticeable formation of nascent litharge on the top of the vessel. The presence of nascent litharge can be detected by the appearance of a black liquid on the top of the vessel.

The yellow dross, which is removed from the top of the vessel, will contain both tin and lead, and will normally average about four weight percent of tin. Such dross can be sold on a tin and lead content basis, or may 3,041,162 Patented June 26, 1962 ice be treated, as by known techniques, to separate the tin from the lead.

When allof the yellow dross has been skimmed ofi the top of the vessel, the separation of antimony from the lead by the process of the present invention is undertaken.

This comprises oxidation with air at a temperature of natively, other lead materials, such as clean, dry battery plates (without separators or lugs) may be utilized. Such materials comprise antimonial lead materials. Such antimonial lead material will absorb antimony from the molten lead within the air-agitated vessel, and will replace the same with lead.

The antimonial lead material, preferably in finely divided form, should be applied to the surface of the molten lead after any yellow, dry dross comprising tin has been skimmed off. The formation of a black liquid at the top of the molten lead will signal the formation of nascent litharge.

The antimonial lead material on the surface of the molten lead will slag-up as the antimonial lead is exposed to air oxidation at the temperature of about l275 'Fl to 1285 F. Thus, air may be introduced to the molten lead from equidistantly spaced pipes discharging towards the surface of the molten lead at a point below the surface of the molten lead; The resultant slag should be removed by skimming. After each skimming opera-' tion, the molten lead should again be covered with antimonial lead material, such as flue dust, and this opera tion should be repeated until no further slag forms.

I have determined that for a 50,000 pound charge of molten lead, the antimonial removal by slag formation with an antimonial lead material such as flue dust may be accomplished within about twelve hours. The flue dusts used by me contain about five weight percent of antimony prior to being added to the surface of the molten lead.

I have determined that the aforesaid process will produce a lead consisting of 99.75 weight percent lead and 0.25 weight percent antimony.

Refining of the antimonial slag removed from the molten lead as by treatment in a furnace without flux will produce an antimonial lead containing about 18 weight percent of antimony.

The slag formed from the addition of the flue dust to the molten lead will be a coal black sla having the hardness of coal and with a rough and uneven surface.

In order to remove the 0.25 weight percent of antimony remaining within the lead, five pounds of flake caustic soda per 50,000 pound charge may be added to the molten lead after it has been cooled to a temperature of about 950 F. This will cause a small amount of liquid to be formed on the surface of the molten lead after about one to one and a half hours agitation. Such liquid should be removed by the addition of sawdust or lime. In this manner lead of substantially weight percent purity may be achieved.

I have found that it is necessary for the satisfactory removal of antimony that nascent litharge be formed, and that the same be at a temperature of about 1,275 F. to 1,285 F. It is my present belief based upon all of the data known to me that only nascent litharge at this temperature will combine with antimony to form a slag to an extent suflicient to effect the removal of the antimony to the level of a 99.75 weight percent pure lead.

A wide variety of vessels may be used as apparatus in the subject invention. I have found that drum-shaped 3 kettles having four equidistantly positioned compressed air inlet pipes at thebottom thereof, and having a capacity for receiving a 50,000 pound charge of antimonial lead from the furnace to be most satisfactory.

The mechanism of the subject invention appears to be that powdereddeadrnaterial'on the surface of the molten lead serves as a seed about which the nascent litharge is" formed'in the presence of .oxygenat the-temperature of about1275" F. to 1285 F. The nascent litharge then removes antimony from the molten lead, and then forms a slag. The powdered lead material apparently serves largely as a catalyst to induce the formation of the nascent litharge.

A wide variety of source materials may be utilized to produce the pure lead obtained in the present process. Thus, any of the conventional charges sent to a lead blast furnace may be utilized.

The slag from the antimony separation may be processed in a furance (Without flux or with a very minor amount of iron or lime flux) to produce an 82 weight percent lead-'18 weight percent antimony mixture as-aforesaid. This enables the refiner to regulate the amount of antimony in lead should he choose to do so. Thus, blending of the pure lead with the 18 weight percent antimonial lead permits closely regulated lead-antimony mixtures tobe obtained.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. A process for purifying lead containing zinc, copper, tin and antimony contaminants which comprises melting such contaminated lead, removing the zinc, copper, and tin contaminants, then forming nascent litharge at the surface of the molten antimony-containing lead which is free of zinc, copper, and tin contaminants at a temperature of about 1275 F. to 1285 F. by the addition of a material which is substantially lead, forming an antimony enriched litharge slag from said lead material by passing oxygen through said molten antimony-containing lead at said temperature of about 1275 F. to 1285" F., and withdrawing said antimony enriched litharge slag.

2. A process in accordance with claim 1 in which the temperature is about 1280 F. p

3. A process in accordance with claim 1 in which the nascent litharge is formed from flue dust derived from a lead smelting blast furnace.

4. A process in accordance with claim 1 in which the zinc,. copper, and tin contaminants are separated from the contaminated lead in that order.

5. A process in. accordance with claim 1 in which the antimony enriched litharge slag is Withdrawn until the molten lead contains approximately 0.25 weight percent antimony.

References'Cite'd in the file of this patent UNITED STATES PATENTS Re. 18,930 Davis Aug. 29, 1933 50,800 Crooke Nov. 7, 1865 1,535,743 Stannard et a1. Apr; 28, 1925 2,217,981 Hallows Oct. 15, 1940 FOREIGN PATENTS 13,068 Great Britain 1891' OTHER- REFERENCE-S Handbook of' Chemistry and Physics, 41st edition, 19597-1960, Chemical-Rubber Publishing Co., Cleveland, Ohio. Pages 594-595'relied on. 

1. A PROCESS FOR PURIFYING LEAD CONTAINING ZINC, COPPER, TIN AND ANTIMONY CONTAMINANTS WHICH COMPRISES MELTING SUCH CONTAMINATED LEAD, REMOVING THE ZINC, COPPER, AND TIN CONTAMINANTS, THEN FORMING NASCENT LITHARGE AT THE SURFACE OF THE MOLTEN ANTIMONY-CONTAINING LEAD WHICH IS FREE OF ZINC, COPPER, AND TIN CONTAMINANTS AT A TEMPERATURE OF ABOUT 1275*F. TO 1285*F. BY THE ADDITION OF A MATERIAL WHICH IS SUBSTANTIALLY LEAD, FORMING AN ANTIMONY ENRICHED LITHARGE SLAG FROM SAID LEAD MATERIAL BY PASSING OXYGEN THROUGH SAID MOLTEN ANTIMONY-CONTAINING LEAD AT SAID TEMPERATURE OF ABOUT 1275*F. TO 1285*F., AND WITHDRAWING SAID ANTIMONY ENRICHED LITHARGE SLAG. 